<?php
/**
 * Removal of everything the plugin stored, run when the plugin is deleted.
 *
 * @package Kordiam
 */

declare( strict_types=1 );

namespace Kordiam;

use Kordiam\Auth\TokenTable;
use Kordiam\Import\RemoteListsServiceProvider;
use Kordiam\Support\MetaKeys;
use Kordiam\Support\Options;
use wpdb;

// Exit if accessed directly.
if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * Deletes the plugin's own options, meta and table.
 *
 * Deliberately leaves Desk-Net's data (needed to revert) and all posts and attachments alone.
 */
final class Uninstaller {

	/**
	 * Sites processed per query when running on a network.
	 *
	 * @var int
	 */
	private const SITES_PER_BATCH = 100;

	/**
	 * Rows deleted per query, to avoid one long-locking unbounded DELETE.
	 *
	 * @var int
	 */
	private const ROWS_PER_BATCH = 1000;

	/**
	 * Database handle.
	 *
	 * @var wpdb
	 */
	private wpdb $db;

	/**
	 * Constructing the uninstaller.
	 *
	 * @param wpdb|null $db Database handle, defaulting to the global one.
	 */
	public function __construct( ?wpdb $db = null ) {
		global $wpdb;

		$this->db = $db ?? $wpdb;
	}

	/**
	 * Removing the plugin's data from every site it was used on.
	 */
	public static function run(): void {
		$uninstaller = new self();

		if ( is_multisite() ) {
			$uninstaller->clean_network();
		} else {
			$uninstaller->clean_site();
		}

		// User meta is network-wide, so it is cleared once.
		$uninstaller->delete_user_meta();
	}

	/**
	 * Removing the plugin's data from every site on the network.
	 */
	private function clean_network(): void {
		$offset = 0;

		while ( true ) {
			$site_ids = get_sites(
				array(
					'fields' => 'ids',
					'number' => self::SITES_PER_BATCH,
					'offset' => $offset,
				)
			);

			if ( array() === $site_ids ) {
				return;
			}

			foreach ( $site_ids as $site_id ) {
				switch_to_blog( (int) $site_id );

				$this->clean_site();

				restore_current_blog();
			}

			$offset += self::SITES_PER_BATCH;
		}
	}

	/**
	 * Removing the plugin's data from the current site.
	 */
	private function clean_site(): void {
		wp_clear_scheduled_hook( RemoteListsServiceProvider::REFRESH_ACTION );

		$this->delete_options();
		$this->delete_post_meta();

		$table = new TokenTable( $this->db );

		$table->drop();
	}

	/**
	 * Deleting the plugin's options, including its transients.
	 */
	private function delete_options(): void {
		$prefix = $this->db->esc_like( Options::PREFIX ) . '%';

		$patterns = array(
			$prefix,
			$this->db->esc_like( '_transient_' . Options::PREFIX ) . '%',
			$this->db->esc_like( '_transient_timeout_' . Options::PREFIX ) . '%',
		);

		foreach ( $patterns as $pattern ) {
			// phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- Bulk delete by name pattern; no core API takes a pattern, and the object cache is flushed below.
			$names = $this->db->get_col(
				$this->db->prepare(
					'SELECT option_name FROM %i WHERE option_name LIKE %s',
					$this->db->options,
					$pattern
				)
			);

			if ( ! is_array( $names ) ) {
				continue;
			}

			foreach ( $names as $name ) {
				delete_option( (string) $name );
			}
		}
	}

	/**
	 * Deleting the post meta the plugin wrote, by exact key so site fields sharing a prefix survive.
	 */
	private function delete_post_meta(): void {
		foreach ( MetaKeys::post_meta_keys() as $meta_key ) {
			$this->delete_meta_rows( $this->db->postmeta, 'post_id', $meta_key );
		}

		wp_cache_flush();
	}

	/**
	 * Deleting the user meta the plugin wrote.
	 */
	private function delete_user_meta(): void {
		foreach ( MetaKeys::user_meta_keys() as $meta_key ) {
			$this->delete_meta_rows( $this->db->usermeta, 'user_id', $meta_key );
		}

		wp_cache_flush();
	}

	/**
	 * Deleting every row holding one meta key, a batch at a time.
	 *
	 * @param string $table       Meta table name.
	 * @param string $id_column   Name of the object ID column, used only to keep the LIMIT deterministic.
	 * @param string $meta_key    Key to delete.
	 */
	private function delete_meta_rows( string $table, string $id_column, string $meta_key ): void {
		do {
			// phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- Bulk delete of one meta key on uninstall; delete_metadata() would run one query per object, and the cache is flushed by the caller.
			$deleted = $this->db->query(
				$this->db->prepare(
					'DELETE FROM %i WHERE meta_key = %s ORDER BY %i ASC LIMIT %d',
					$table,
					$meta_key,
					$id_column,
					self::ROWS_PER_BATCH
				)
			);
		} while ( is_int( $deleted ) && $deleted >= self::ROWS_PER_BATCH );
	}
}